The present invention generally relates to explosives and more particularly to a primer charge.
The smallest component in small arms ammunition, the percussion primer, is the link between the striking of the firing pin and the explosion of the projectile out of the cartridge casing. Percussion primers or primer mixes generally have undergone only gradual changes since their original development. For a time, mercury fulminate was the most commonly used primer mix. In the 1920s, alternate priming mixes were found to replace mercury fulminate, as this latter composition was found to deteriorate rapidly under tropical conditions and cause potential health problems or concerns such as lethargy and nausea to the shooter after firing. However, the alternate mixes, based on lead thiocyanate/potassium chlorate formulations were soon recognized as detrimental to weapon barrels because of the formation of corrosive water soluble potassium chloride salts upon combustion. Later primer mixes were based on the primary explosive lead styrphnate, a substance which is much more stable than mercury fulminate and is still in use today.
Except for the use of pure mercury fulminate as an igniter, most commonly used primer mixes are chemical mixtures comprising at least a primary explosive, an oxidizing agent and a fuel source. Lead styphnate is the most common primary explosive, with tetrazene typically being added as a secondary explosive for rendering the lead styphnate composition sufficiently sensitive to percussion. The most common oxidizing agent is barium nitrate, which is combined with a fuel, antimony sulfide. Friction producing agents and additional fuels are also added. Unfortunately, lead, antimony and barium are highly toxic, and therefore pose a potential health hazard, particularly when used within an enclosed shooting range where they can accumulate in the atmosphere and on surfaces.
Accordingly, attempts have produced a non-toxic primer composition. The phrase xe2x80x9cnon-toxicxe2x80x9d is intended to mean a substance consisting essentially of materials which are not toxic heavy metals such as lead or barium, known carcinogens or poisons, especially when vaporized, burnt or exploded as in the firing of an ammunition round. In the product ion of non-toxic primer mixes, diazodinitrophenol (DDNP) is often a preferred substitute for lead styphnate as the primary explosive. DDNP is both slightly insoluble in water and is desensitized by water for safer processing. Like lead styphnate, DDNP typically is accompanied by tetrazene as a secondary primary explosive to render the composition sufficiently sensitive to percussion.
While considerable attention has been directed to removing lead from primer mixes, there has been less attention paid to the removal of remaining toxic components from the primer mix. Thus, toxic oxidizing agents and fuels, such as barium nitrate and antimony sulfide, still remain sources of concern. Both barium and antimony are highly toxic metals and their inclusion in the primer mix creates a toxic residue after firing. Accordingly, there exists a need for a non-toxic primer mix free of both lead and toxic oxidizers and fuels such as barium nitrate and antimony sulfide.
The present invention generally comprises a composition and method of preparing a non-toxic primer mix including in one embodiment both bismuth sulfide and potassium nitrate as the pyrotechnic portion of the primer mix. In a further embodiment, zinc sulfide and aluminum nitrate are included as the pyrotechnic portion of the primer mix. Bismuth sulfide and zinc sulfide serve as non-toxic fuels for the non-toxic oxidizers of potassium nitrate and aluminum nitrate in the production of an ignition flame.
In greater detail, the non-toxic primer mix contains approximately 2-20% by weight bismuth sulfide, approximately 25-70% by weight potassium nitrate and approximately 25-50% by weight of a lead-free explosive material. Additionally, the primer can include additional fuels such as nitrocellulose, aluminum, manganese and manganese oxide. Furthermore, pentaerythritol tetranitrate (PETN) may be included as a primary explosive and gum arabic used as a binder.
The primer mix typically is wet processed during production for safety, and comprises the steps of combing water and on a dry weight percent approximately 20% by weight bismuth sulfide, approximately 25-70% by weight potassium nitrate, and approximately 25-50% by weight explosive material and then mixing. The wet formed primer mix can then be rolled and charged into percussion cups.
In an additional embodiment, the non-toxic primer mix contains approximately 2-20% by weight zinc sulfide, approximately 25-70% by weight aluminum nitrate and approximately 25-50% by weight of a lead-free explosive material. Additionally, the primer can include additional fuels such as nitrocellulose, aluminum, manganese and titanium. Furthermore, pentaerythritol tetranitrate (PETN) maybe included as a primary explosive and gum arabic used as a binder.
In a further embodiment, the primer mix is wet processed comprising the steps of combing water and on a dry weight percent approximately 2-20% by weight zinc sulfide, approximately 25-70% by weight aluminum nitrate, and approximately 25-50% by weight explosive material and then mixing. The wet formed primer mix can then be rolled and charged into percussion cups.